OBJECTIVE & APPROACH: We propose to isolate and characterize the DNA polymerases found in human milk and in human breast cancer cells. Isolation of the DNA polymerases will be accomplished using column chromatographic methods. DNA polymerase characterization studies will include: (1) Determination of template primer utilization specificities. (2) Molecular weight determinations. (3) Divalent cation requirements. (4) Antibody enzyme inhibition studies using antibody to purified human cellular type DNA polymerase I and a variety of purified primate viral DNA polymerases. (5) Determination of the ability of any isolated DNA polymerase to transcribe heteropolymeric region 60-70 S viral RNA. If a viral type DNA polymerase is isolated from some human milk samples consideration will be given to the development of a radioimmune assay for use in extended epidemiological studies to determine the frequency of expression of this type enzyme in the human population.